Cognitive dysfunction in the aging and elderly Veteran population confers a risk for increased mortality. Cognitive deficits are prevalent in neurodegenerative disorders, like Alzheimer?s disease, stroke, and depression. More recently, obstructive sleep apnea (OSA) has been recognized as a factor contributing to cognitive deficits via intermittent hypoxia and sleep fragmentation. Moreover, chronic lung disease, particularly COPD, is also thought to be related to cognitive decline, possibly through sleep fragmentation and hypoxic injury to the brain. Our pilot project data on the impact of OSA-COPD Overlap Syndrome in older Veterans provides evidence that the presence of comorbid OSA and COPD does contribute to sleep disturbances, impairment in certain domains of cognitive function and an overall reduced quality of life (QoL). Given that PAP therapy has been shown to improve neurocognitive function and sleepiness in moderate to severe OSA, probably by reducing arousals and hypoxia, as well by improving sustained hypoxia due to COPD, it will likely also have a positive impact on sleep and cognitive impairment in patients with moderate to severe degree of Overlap Syndrome. The results from the pilot project speak to the feasibility of conducting a future longer study of the impact of treatment with positive airway pressure therapy (PAP) vs. conservative care in older Veterans with Overlap Syndrome. Our future project builds on the pilot data to study the following aims: Aim1 will investigate the effect of PAP therapy vs. conservative care for 6 months on daytime sleepiness and sleep quality in older Veterans with OVS. Aim 2 will study the effect of PAP vs. conservative care for 6 months on neurocognitive function older Veterans with OVS. Aim 3 will determine the effect of PAP vs. conservative care for 6 months on QoL in older Veterans with OVS. The approach will be a prospective parallel group randomized controlled study, wherein we will administer sleep and QoL questionnaires, and a battery of cognitive tests, before and after 6 mo of PAP therapy or conservative management to evaluate the above outcomes. Our goal is to enhance rehabilitation from comorbid chronic conditions that frequently impact sleep and cognitive function, with the ultimate objective of improving the overall health and quality of life of elderly Veterans suffering from these disorders.